Healthy soil and sustainable growing

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American Journal of Alternative Agriculture
http://eap.mcgill.ca/MagRack/AJAA/AJAA_8.htm
 
Restoring the productivity of marginal soils with organic amendments
Sharon B. Hornick and James F. Parr

Abstract. The mining of sand and graver deposits and excavation of topsoil
in urban areas have left extensive tracts of exposed subsoils that do not
support plant growth because of adverse soil chemical and physical
properties Such degraded and marginal soils, or spoils, are infertile, low
in organic master, often acidic, and subject to severe erosion and surface
runoff. Many of these lands are owned by small and part-lime farmers who
wish to restore their aesthetic value and agricultural productivity.
Research has shown that with liming and the proper use of organic
amendments such as animal manures and sewage sludge compost, these lands
can be restored to a high lever of productivity in as little as three years
The methods and techniques for improving the productivity of marginal soils
described in this paper can be of considerable benefit to some farmers in
developed and developing countries where there is no other choice but to
farm marginal soils because of the lack of highly productive agricultural
lands. With increased efforts to restore the productivity of degraded and
marginal soils through the use of organic amendments, conservation tillage,
and crop rotations, future research should address the effect of best
management practices on crop yields, the nutritional quality of crops, and
the bioavailability of plant nutrients to both animals and humans.
Introduction

Regular additions of organic materials such as animal manures and crop
residues are of utmost importance in maintaining the tilth, fertility and
productivity of agricultural soils, protecting them from wind and water
erosion, and preventing nutrient losses through runoff and leaching. These
materials have predictable beneficial effects on soil physical properties
such as increased water-holding capacity, soil aggregation, soil aeration
and permeability, and decreased soil crusting and bulk density (USDA, 1957;
1978).

Failure to recycle organic wastes and residues, intensive row crop
production, and lack of sod-based crop rotations can result in extensive
soil degradation and a decline in productivity due to excessive soil
erosion and loss of fertility. The continuing desertification of
Sub-Saharan Africa and the dustbowl of the central U.S. Great Plains in the
1930's can be attributed largely to improper farming methods that neglected
the importance of soil organic master in crop production.

When organic materials, such as compost, animal manures, crop residues and
sewage sludges are used as the primary sources of plant nutrients, the
management system has often been referred to as "organic farming" (USDA,
1980). More recently, the terms alternative, regenerative. low-input, and
sustainable have been used to describe farming systems that recycle
available on-farm organic resources and sometimes off-farm materials such
as municipal wastes, to maintain or improve soil productivity.

In addition, organic materials can be used effectively for land reclamation
purposes. For example, the mining of topsoil and sand and graver deposits
in urban areas has left extensive tracts of exposed, highly erodible
subsoils which are not conducive to the support of plant growth because of
their adverse chemical and physical properties. Such areas detract from the
aesthetic value of an urban environment and are major contributors to
environmental pollution through surface runoff, eutrophication (i.e.,
nutrient enrichment) of lakes and streams and sedimentation from soil
erosion. Thus, there is a need to develop sound practices for restoring the
productivity and value of these lands in the most economic and expedient
way.

A wide variety of different organic wastes and residues can be used as soil
conditioners and sources of plant nutrients on agricultural soils, with
little or no adverse effects on public health and the environment. The
purpose of this paper is to discuss how some organic amendments can provide
an effective means of restoring the productivity of marginal, degraded, and
infertile soils and how changes in cultural practices may affect crop
quality.
Reclamation of degraded and marginal soils

Some of the areas mined for sand and gravel in the northeast corridor of
the United States are owned by small farmers who, after mining operations
are completed, want to revegetate the barren areas to minimize erosion and
improve the aesthetic value of the land. Som~ want to put the land back
into agricultural production so as to gain a more favorable (i.e., lower)
tax assessment.

Research was conducted by the USDA Agricultural Research Service beginning
in the late 1970's to determine the feasibility and practicability of re
vegetating these spoiled lands. After mining, the residual spoil materials
were generally acidic (pH 4.5), of sandy texture and lacking sufficient
organic matter and nutrients to maintain plan growth. For two years, 0, 40,
80 and 16 mt/ha of feedlot manure and sewage sludge compost produced by the
Beltsville Aerated Pile Method (Willson et al., 1980) were applied to spoil
area plots and incorporated by rototilling. All treatments were replicated
three times. Table 1 shows that after two cropping years with sweet corn
and two repeated applications of each waste, both the soil organic master
and gravimetric water content increased significantly. Additions of 160
metric tons per hectare of either compost or manure increased the organic
master content from an initial lever of 0.8 percent to 4.2 percent and 8.5
percent, respectively. Gravimetric water content was similarly affected,
increasing from 7 percent for the control soil, which received only the
recommended rate of commercial inorganic fertilizer for sweet corn, to 15
percent and 32 percent for the 160 mt/ha rate of compost and manure,
respectively. Initially the manure contained twice as much water (80
percent by weight) as did the compost (40 percent by weight), but the
larger increase in the soil water content for the manure-treated plots
versus the compost-treated plots was attributed to the fact that the manure
had a higher water-holding capacity than did the compost.

These changes in soil physical properties are important, because the
increased lever of organic master increased the soil's capacity to retain
more plant nutrients, including water, resulting in increased crop growth
and yield. During drought conditions, sweet corn grown on the
manure-treated plots showed fewer signs of moisture stress (wilting and
rolling of leaves) than did the compost-treated plots, again indicating the
higher water-holding capacity of the manure over compost.

With sandy soils, high afternoon temperatures can dry out newly planted
seeds and, therefore, reduce cotyledon emergence and seedling survival.
Soil temperatures taken at a 4-inch depth on plots receiving either 160
mt/ha of compost or manure were consistently 5 to 10 degrees Fahrenheit
longer than on the unamended control soils (Hornick, 1982a). The magnitude
of temperature lowering was directly related to application rate of the
organic material. Such a reduction in temperature may not be desirable in
heavy soils in cool regions because of possible adverse effects on seed
germination. There was considerably less erosion on those plots treated
with manure or compost because of an improvement in soil physical
properties, particularly soil structure . This was evidenced by visible
gullying in the control plots.

Significant increases in corn stalk yields were noted for plots treated
with compost and manure (Table 2). However, sweet corn ear yields were not
always improved by additions of organic materials (Hornick, 1982a). Sahs
and Lesoing (1985) also noted similar results when corn was grown with
synthetic fertilizer versus feedlot manure. For corn grown on
manure-treated plots they found significantly higher yields in a drought
year, but significantly longer than normal yields in years of average
temperature and adequate rainfall. Similar results and observations were
also cited by the USDA study team on organic farming (USDA, 1980).

The most dramatic increase in crop yield occurred when green snap bush
beans were grown on plots receiving 0, 40 and 80 mt/ha of sewage sludge
compost (Table 2). The yields of green beans receiving 40 and 80 mt/ha of
compost were 34 percent and 49 percent higher, respectively, than the
yields on the control plots (Hornick, 1982a, 1982b). In these studies, as
well as those discussed earlier for sweet corn, the productivity of the
sand and graver spoils was restored. to a relatively high lever in two to
three years.
Soil management and environmental considerations

An important concept that is often overlooked is that for most agricultural
soils, degradative processes such as soil erosion, nutrient runoff losses,
and organic master depletion are going on simultaneously with conservation
practices such as residue management, crop rotations, and conservation
tillage. The potential productivity of a particular soil then depends on
the interaction of degradative processes and conservation practices (Figure
1; Parr and Meyer, 1987). On our best agricultural soils, e.g.,
gently-sloping, medium-textured, well-structured, and deep-profile, a high
level of productivity can be maintained by a relatively few, but essential,
conservation practices that can readily offset most degradative processes.
However, on marginal soils, e.g., steeply-sloping, coarse-textured,
poorly-structured, shallow-depth, and low fertility, soil conservation
practices must be maximized to offset further degradation. The vital
component in this dynamic equilibrium is organic matter.

Organic matter can be supplied to marginal soils from a number of sources
including (1) on-farm wastes such as animal manures and crop residues, as
well as green manure crops or (2) off-farm wastes such as sewage sludge and
composted refuse. Off-farm wastes can be important sources of organic
matter to farmers who do not have sufficient animals or cropping area to
produce the amount of manure and crop residues needed to maintain soil
productivity.

The plant nutrient contents of most organic materials are generally much
lower than those supplied by commercially available chemical fertilizers.
For example, the macronutrient content of crop residues can range from 0.7
to 2.5 percent for nitrogen, 0.07 to 0.2 percent for phosphorus and 0.9 to
1.9 percent for potassium; animal manures can range from 1.7 to 4 percent
for nitrogen, 0.5 to 2.3 percent for phosphorus, and 1.5 to 2.9 percent for
potassium (USDA, 1978); while sewage sludges range from 3 to 7 percent for
nitrogen, 1 to 3 percent for phosphorus and 0.2 to 3 percent for potassium
(Hornick et al., 1984).

Organic materials can differ widely in their properties and
characteristics. Some materials, such as uncomposted animal manures, green
manures, and sewage sludges, are subject to rapid microbial decomposition
(i.e., mineralization) in soils and tend to release their plant nutrients
rapidly. This is desirable for soils that are already at a relatively high
lever of fertility and productivity. On the other hand, some other
materials, such as cereal straws, wood bark, and composted animal manures
and sewage sludges, would be more resistant to microbial attack and release
their nutrients at a relatively slower rate. This higher lever of organic
stability provides a distinct advantage in the initial reclamation of
marginal soils because it imparts a beneficial and long-term residual
improvement of soil physical properties. Unless the physical nature of
these soils is improved first, the plant Use efficiency of nutrients,
whether from organic amendments or chemical fertilizers, will be
unacceptably low (Parr et al., 1986).

In many developing countries there is a scarcity of suitable organic
materials for composting or direct recycling on agricultural lands because
of competitive uses. Thus, treating the entire soil-root zone with an
organic amendment is often not feasible because of limited amounts of
material. Consequently, the farmer must seek colt-effective methods of
utilizing these materials to enhance soil productivity and crop yields. It
is noteworthy that the productivity of marginal lands can be improved
substantially with relatively small amounts of materials. This can be
accomplished through localized placement techniques such as side-dressing,
banding, bed and furrow systems, vertical mulching (Parr, 1959) and
slot-mulching (Saxton et al., 1981).

Composting or co-composting an organic waste results in a more stable
product that is easier to store and use. Co-composting of wastes that vary
widely in their carbon to nitrogen ratios or solids content may produce a
higher quality product and allows recycling of some wastes that could not
be utilized as the only source of organic master due to some inherent
chemical or physical property (Parr et al., 1986). Possible wastes that
could be co-composted are municipal refuse or garbage, pit latrine wastes,
sewage sludges, animal manures and crop residues.

Fertilizer use efficiency can be very low in strictly monoculture systems
or where organic recycling is not practiced. This inefficiency allows for
the movement of nutrients through the soil profile and into the "round
water. Due to heavy use of pesticides and nitrogen fertilizer,
contamination of "round water is evident in our major agricultural areas
(Hallberg, 1986; 1987). The possibility of Federal and State regulatory
agencies enacting legislation to control these chemical inputs is also a
major concern to the agricultural community.

Many farmers have already pulled back from their long-held goal of
achieving maximum yields because of the costly production inputs and low
market prices which have steadily decreased their profitability. The
recycling of organic wastes can longer production inputs by decreasing the
amount of chemical fertilizer required for crop growth with minimal adverse
environmental impact. As this change in cultural practice occurs, the
effect of various longer fertilizer levers on crop quality could become
very important.
Crop quality and nutritional considerations

Although there are many factors that can affect crop quality, the cultivar
and post-harvest handling are considered to have the greatest effect on the
nutrient composition of crops (Harris, 1975; Kader, 1987). One is reminded,
however, that cultivars are often selected for their response to production
inputs, especially chemical fertilizers, and with maximum crop yields as
the primary consideration. As farmers attempt to reduce their dependency on
chemical fertilizers and pesticides, they will undoubtedly adopt various
cultural practices to fulfill the plant nutrient requirement and to control
weeds and insects. Thus, cultural practices could have considerable impact
on crop quality both now and in the future.

There has been much speculation on the benefits of consuming crops grown
conventionally with chemical fertilizers compared with those grown on soils
amended with organic materials as the primary source of plant nutrients.
For example, researchers have shown conflicting results with respect to the
ascorbic acid (vitamin C) content of crops. Kansal et al. (1981) showed
that as the lever of farmyard manure increased, the ascorbic acid content
of spinach decreased. On the other hand, Schuphan (1974) reported higher
ascorbic acid values for spinach grown on manure treated soil compared with
chemical fertilizer. Similarly, Harwood (1984), using Pak Choi, and Ahrens
et al. (1983), using spinach, also showed higher levers of ascorbic acid
with increasing rates of composted manure versus chemical fertilizer.

The results of an NPK factorial experiment conducted to determine whether
the results observed for ascorbic acid were due mainly to an organic
amendment, or simply a fertilizer effect based on the nitrogen content of
each amendment showed a significant decline in ascorbic acid content of
kale as the rate of inorganic nitrogen increased (Hornick and Lloyd, 1986).
These results indicate that increased nitrogen rates do tend to depress
ascorbic acid levels. While this may be attributed in part to a dilution
effect from increased yields, other biochemical interactions appear to be
involved.

Most of the conflicting results that have been reported on crop response to
chemical and organic fertilizers are most likely due to the fact that the
organic materials were mineralizing at different rates, thus, providing
different levers of inorganic nitrogen to the crop. More-over, it is
possible that results were influenced by the predominance of a particular
form of inorganic nitrogen i.e., nitrate (NO3 ) or ammonium (NH4 ), that
was taken up by the plant. In a review of possible fertilizer effects on
crop quality, Grunes and Allaway (1985) noted that the addition of boron to
boron deficient soils increased the carotene (a vitamin A precursor)
content in carrots and speculated that fertilizers that correct chlorosis
in plants may increase the carotene content of the plant. This concept is
especially interesting in light of the fact that after basic needs for
protein and calories are satisfied, the lack of a suitable source of
vitamin A is one of the biggest health problems in developing countries.
Perhaps with the addition of boron or through some other management factor
we may also increase the lever of carotene or some other nutrient that is
presently deficient in native diets.

Recently we have become increasingly concerned about "round water quality
and the increased levers of nitrates and pesticides that have been reported
in our major agricultural areas (Hallberg, 1987). Some states have already
developed strategies for reducing the recommended rates of fertilizer
nitrogen to minimize the risk of "round water pollution. It would indeed be
ironic if it was shown that longer rates of fertilizer N were related to
crops of a higher nutritional value.
Bioavailability

The concept of producing better quality crops, however, is a complex issue
because bioavailability of crop nutrients depends on many factors.
Bioavailability refers to the amount of a particular nutrient that is
absorbed from a food after consumption that is utilized by an animal or
human It is not the total amount of a nutrient in the food that is
consumed. Measurements of nutrient bioavailability are difficult because of
the many interactions that occur between minerals, vitamins and food
components such as fiber. For example, iron bioavailability is determined
by the iron status of the individual and the source of - iron being
consumed. It is enhanced by the presence of ascorbic acid (vitamin , C) in
the meal. In addition, iron bioavailability may decrease when a meal high
in dietary fiber is consumed by an individual who does not normally consume
a large amount of dietary fiber. Therefore, each of these nutrients, iron,
ascorbic acid, and fiber is important in the diet for optimum health and
normal bodily function, but the presence of one might enhance or impair the
function of the other.

In addition to these types of interactions, little is known about the
bioavailability of nutrients in crops grown under different management
conditions. At the 1st International Symposium on Horticulture and Human
Health held in 1987 in Virginia, it was very apparent how little the
horticulturalists and nutritionists knew about the practices and needs of
one another. It is clear that research on cultural practices and
bioavailability of nutrients in foods and feeds consumed by humans and
animals is needed, and should be conducted by multidisciplinary teams
including soil scientists, agronomists, horticulturalists, crop breeders,
physiologists, and nutritionists.
Summary

Marginal, infertile farm soils exist throughout the world. Many of the
soils in developing countries are similar to those of sand and graver spoil
areas in that they are low in organic master content and nutrients and
occur in aria, harsh environments. These soils can be made productive if
the soil degradation processes are offset by appropriate soil
conservation/reclamation practices.

Many of the farms are very small and have limited available resources. Even
so, composted animal manures and wastes can be utilized effectively by
using selective placement techniques such as side-dressing of plants or
seeding directly into a compost-treated zone. This type of localized
placement will provide maximum benefit of the material as a soil
conditioner and as a source of plant nutrients and ultimate utilization of
the limited amount of available resources.

After restoration of marginal soils, it is very important that small
amounts of organic materials are available each year to maintain soil
productivity. As a rule, wherever people live there is a source of waste
materials that could be utilized advantageously as organic amendments for
agricultural soils. Even people in remote areas, on small farms, on farms
without animals, and in the aria regions of developing countries can
utilize the idea of cg-composting to recycle their human wastes and refuse.
Because composting is a thermophilic process, it inactivates certain
pathogens and a reduction in the incidence of parasitic infestation and
enteric diseases may also be accomplished. In addition, composting provides
a stabilized form of organic master that has a longer residence time in
soil compared with raw wastes which can decompose very rapidly, especially
under the extreme climatic conditions of the aria regions.

Regular additions of organic materials to soils can reduce erosion and
nutrient runoff losses, improve soil structure, increase water-holding
capacity, longer soil temperatures, provide a source of plant nutrients,
and increase the crop use efficiency of chemical fertilizer. Further
research is needed to characterize the interaction of organic amendments,
soil type, climate, and the crop to improve our estimates and predictions
of soil tilth, fertility, and productivity. In so doing, we can achieve a
practical and workable balance between degradation processes and
conservation practices to maintain a productive soil with minimal
environmental pollution.

In our efforts to increase a farmer's net returns, we have emphasized the
use of heavy and costly off-farm production inputs such as fertilizers and
pesticides to produce maximum yields of unflawed fruits and vegetables for
American consumers. In some cases, "round water pollution has resulted and
in others, the heavy production inputs are no longer profitable. Initial
research indicates that longer nitrogen rates can produce higher quality
crops with respect to ascorbic acid content. Because of environmental
concerns, we may need to change our soil management practices, even though
longer yields may result.

Further research by multidisciplinary groups could elucidate the effect of
fertilizer rates and sources on crop quality and resulting nutrient
bioavailability, and the feasibility of utilizing this new information for
production of crops of greater nutritional value in both developed and
developing countries. In addition, such information would be particularly
attractive to farmers producing fruits and vegetables for urban consumers,
who would be willing to pay a premium for produce grown with limited
chemical input. For low input farmers with limited capital, this may be a
particularly viable option.
References

1. Ahrens, E., S. Elsaidy, 1. Samaras, F. Samaras, and E. Wistinghausen.
1983. Significance of fertilization for the post-harvest condition of
vegetables, especially spinach. In: Environmentally Sound Agriculture,
William Lockeretz (ed.). pp. 239-246. Praeger, New York.

2. Grunes, D. L., and W. H. Allaway. 1985. Nutritional quality of plants in
relation to fertilizer use. In: Fertilizer Technology and Use, O. P.
Engelstad et al. (eds.). pp. 589-619. Soil Science Society of America,
Madison, Wisconsin.

3. Hallberg, G. R. 1986. From hoes to herbicides: Agriculture and
groundwater quality. J. of Soil and Water Conservation 41:357-364.

4. Hallberg, G. R. 1987. Agricultural chemicals in groundwater: Extent and
implications. Amer. J. Alternative Agriculture 2(1):3-15.

5. Harris, R. S. 1975. Effects of agricultural practices on the composition
of foods. In: Nutritional Evaluation of Food Processing, R. S. Harris and
E. Karmas (eds.). pp. 33-57. Second ed., AVI Publishing Company, Westport,
Connecticut.

6. Harwood R. R. 1984. Organic farming research at the Rodale Research
Center. In: Organic Farming: Current Technology and Its Role in a
Sustainable Agriculture, D. F. Bezdicek et al. (eds.). pp. 1-17. ASA, CSSA,
and SSSA, Madison, Wisconsin.

7. Hornick, S. B., J. J. Murray, and R. L. Chaney. 1980. Overview on
utilization of composted municipal sludges. In: Natl. Conf Munic. and
Indus. Sludge Composting Proc. pp. 15-22. Inform. Transfer, Inc., Silver
Spring, Maryland.

8. Hornick, S. B. 1982a. Crop production on waste amended graver spoils.
In: Land Reclamation and Biomass Production with Municipal Wastewater and
Sludge, W. E. Sopper et al. (eds.). pp. 207-218. Pennsylvania State
University Press, University Park, Pennsylvania .

9. Hornick, S. B. 1982b. Organic wastes for revegetating marginal lands.
Biocycle 23(4):42-43.

10. Hornick, S. B. 1983. Animal wastes. In: Land Treatment of Hazardous
Wastes, J. F. Parr et al. (eds.). pp. 276-280. Noyes Data Corporation, Park
Ridge, New Jersey.

II. Hornick, S. B., and C. A. Lloyd. 1986. Fertilizer effects on crop fiber
and nutrient content. Agronomy Abstracts, p. 202.

12. Hornick, S. B., L. J. Sikora, S. B. Sterrett, J. J. Murray, P. D.
Millner, W. D. Burge, D. Colacicco, J. F. Parr, R. L. Chaney, and G. B.
Willson. 1984. Utilization of sewage sludge compost as a soil conditioner
and fertilizer for plant growth. Agriculture Information Bulletin No. 464.
U.S. Department of Agriculture, U.S. GPO, Washington, DC. 32 pp.

13. Kader, A. A. 1987. Influence of pre-harvest and postharvest environment
on nutritional composition of fruits and vegetables. In: Proceedings of Ist
International Symposium on Horticulture and Human Health, April, 1987. (In
Press). Amer. Soc. Hort. Sci., Alexandria, Virginia.

14. Kansal, B. D., B. Singh, K. L. Balaj, and G. Kaur. 1981. Effect of
different levers of nitrogen and farmyard manure on yields and quality of
spinach (Spinacea oleracea L.) Qual. Plant. Plant Foods Human Nutrition
31:163-170.

15. Parr, J. F. 1959. Effects of vertical mulching and subsoiling on soil
physical properties. Agron. J. 51:412-414.

16. Parr, J. F. 1982. Composted sewage sludge, a potential resource for
small farms. In: Research for Small Farms, H. W. Kerr and L. Knutson
(eds.). pp. 90-99. USDA, ARS, Misc. Pub. No. 1422, Washington, DC.

17. Parr, J. F., and R. E. Meyer. 1987. Strategies for increasing soil
productivity in developing countries. In: Proceedings of a Workshop on
"Soil, Water and Crop Management Systems for Rainfed Agriculture in
Northeast Thailand." Published by the U.S. Agency for International
Development (S&T/AGR USAID), Washington, DC.

18. Parr, J. F., R. 1. Papendick, and D. Colacicco. 1986 Recycling of
organic wastes for a sustainable agriculture. Bio. Ag. Hort. 3:115-130.

19. Sahs, W. W., and G. Lesoing. 1985. Crop rotation and manure versus
agricultural chemicals in dryland grain production. J. Soil and Water Cons.
40:511 516.

20. Saxton, K. E., D. K. McCool, and R. 1. Papendick 1981. Slot mulch for
runoff and erosion control. I Soil Water Conserv. 36:44-47.

21. Schuphan, W. 1974. Nutritional value of crops a influenced by organic
and inorganic fertilizer treatments--results of 12 years' experiments with
vegetable 3. Qual. Plant. Plant Foods Human Nutrition, 23:333-358.

22. U.S. Department of Agriculture. 1957. Soil--Year book of Agriculture.
U.S. GPO, Washington, DC.

23. U.S. Department of Agriculture. 1978. Improving Soils with Organic
Wastes. Report to the Congress in response to Section 1461 of the Food and
Agriculture Act of 1977 (PL 95-113). U.S. GPO, Washington, DC. 157 pp.

24. U.S. Department of Agriculture. 1980. Report an' Recommendations on
Organic Farming. U.S. GPC Washington, DC. 94 pp.

25. Willson, G. B., J. F. Parr, E. Epstein, P. B. Marsh R. L. Chaney, D.
Colacicco, W. D. Burge, L. J Sikora, C. F. Tester, and S. B. Hornick. 1980.
Manual for composting sewage sludge by the Beltsville Aerated Pile Method.
EPA-600/8-80-022. U.S. GPC Washington, DC. 64 pp.

 

Citation : Hornick Sharon B., Parr James F., 1987, "Restoring the
productivity of marginal soils with organic amendments", Vol. 2, No. 2,
1987, pp. 64-68